Sheet feeding apparatus for printing presses

ABSTRACT

Sheet feed apparatus for printing presses in which sheets are lifted from a stack and transported to a sheet feed device includes a carrier operable between a pick-up position and a feed position. The carrier includes a carrier bar having a central section and two outer sections rotatably mounted relative to the central section. Suction grippers are mounted on the two outer sections and also a suction gripper may be mounted on the central section. A slide bar means is provided for varying the travel pattern of the outer suction grippers such that the latter are operable to align a sheet as the sheet is transported from the stack towards the sheet feed device.

Mute States atent [111 3,809,389 Wirz May 7, 1974 [541 igfffigg ggg gFOR FOREIGN PATENTS OR APPLICATIONS 1,177,652 9/1964 Germany 271/93 [75]Inventor: Arno Wirz, Bammental, Germany [73] Assignee: HeidelbergerDruckmaschinen Prima'y 'f Blunk Amiengeseuschafl, Heildelberg, AssistantExammer-Bruce H. Stoner, Jr. Germany Attorney, Agent, or Firm-Herbert L.Lerner [22] Filed: Dec. 12, 1972 [57] ABSTRACT [21] Appl- 314,338 Sheetfeed apparatus for printing presses in which sheets are lifted from astack and transported to a [30] Foreign Application Priority D t sheetfeed device includes a carrier operable between Dec 18 I971 Gama 12,6308} a pick-up position and a feed position. The carrier iny cludes acarrier bar having a central section and two [52] U S Cl 271/91 271/60271/93 outer sections rotatably mounted relative to the cen- [51] a 9/14tral section. Suction grippers are mounted on the two [58] Fieid 90 107outer sections and also a suction gripper may be mounted on the centralsection. A slide bar means is provided for varying the travel pattern ofthe outer [56] References Cited suction grippers such that the latterare operable to align a sheet as the sheet is transported from the stackUNITED STATES PATENTS towards the sheet feed device. 2,995,360 8/1961Simpson 271/107 3,360,262 l2/I967 Kekopoulos et al. 271/60 x 8 Claims, 4Drawlng Flgllres 'MWTEM 7 291 4 $809389 SHEET 1 BF 3 all FIG: 2

1 SHEET FEEDING APPARATUS FOR PRINTING PRESSES The invention relates toa sheet feeding device for printing machines and more particularly .to asheet feeding device, having conveyor suction grippers for liftingsheets from a stack in which the height of the stack can be adjusted bypneumatically or electrically operated means. The, conveyer suctiongrippers pick up the top sheet from the stack and carry it in onedirection toward further sheet transport means. The conveyor suctiongrippers are pivotally mounted on a carrier bar which has impartedthereto an oscillatory movement by means of an eccentric or cam driveand which is. guided rectilinearly by a slide bar arrangement.

It is an object of the present invention to align a sheet, which isgripped by the conveyer suction grippers in such a manner'during thefeeding movement that the exact placement of the front edge of the sheetagainst the front stops isassured in that the front edge of the sheetdoes not arrive askew.

From the German Patent 1, 177,652 a sheet feeding device is known inwhich two suction grippers are suspended by a shaft having anoscillatory motion and which are guided parallel to the surface of thepile of sheets by means of a control cam. One of the suction grippers ispivoted with respect to the other and is adjustable by means of anadjustable control lever, whereby a lead or lag of the suction surfaceof the pivoted suction gripper relative to the other one may be obtainedduring the feeding motion. The lead or lag of the one suction gripperrelative to the other causes alignment of the sheet being gripped andlifted from the pile during the feeding motion toward the further sheettransport means.

Such alignment means can advantageously be used for smaller sheet sizes.For large sheet sizes, however, the tilting of the gripped sheet aboutone of the two suction grippers has a very detrimental effect in thatthe sheet is also moved in its central region, during its alignment,that is the sheet moves forward or back in its entirety. Thisdisplacement of the sheet in'or toward the transport direction can causeregistration differences in the case of relatively large.corrections,'particularly with the larger sheet sizes, or makenecessary an adjustment of the suction head relative to the machine.

To avoid this disadvantage, in a further sheet feeding device accordingto German Patent 1,786,029, the tube carrying the conveyer suctiondevice is pivoted at its center about a vertical axis and is rigidlyconnected with a lever, the free end of which slides in a U-shaped guidebar which can be adjusted at an angle relative to the direction oftravel. Because the two conveyer suction devices can pivot about avertical axis, the sheet is rotated during its alignment in such amanner that its front edge assumes the desired position without adetrimental displacement of the sheet in the transport direction.

However, this known sheet feeding device has another disadvantage. Forprocessing sheets of larger size, at least a third suction gripper mustbe attached on the conveyer bar, in order to prevent excessive saggingof the sheet being transported. Otherwise, the blower air would beprevented from separating the sheet properly from the pile and fromcarrying it forward, so that its front edge cannot be reliably grippedby the sheet transport means which passes the sheet on. The arrangementof a third suction gripper at the center of the tube carrying the twoconveyer suction gripper, however, interferes with the support of thetube, which must be located at that position.

In the case of larger size sheets, the conveyer suction grippers mustfurthermore be provided at a greater distance from the rear edge, whichleads to a large overhang of the support and guidance members of thecarrier tube of the conveyer suction grippers. If, however, the verticalaxis of the carrier tube support were displaced on the center line ofthe sheet, a lateral dislocation would occur in the alignment of thesheet to be transported and depending on the size of this displacement,the registration of the sheet would also be impaired.

it is an object of the invention to provide a sheet feeding device whichprocesses large sheet sizes in a reliable manner and which makespossible the alignment of the front edge of the sheet during the feedingor transport movement without displacement of the transported sheetinthe transport direction or laterally thereto.

The present invention overcomes the aforementioned prior artdisadvantages by providing at the cen ter of the carrier bar a conveyersuction gripper which is held in vertical position by a slide bar duringthe oscillatory movement of the carrier bar. The carrier bar is dividedinto three sections, the outer sections being rotatable or pivotablymounted on the center section of u the carrier bar and each outersection carrying an additional conveyer suction gripper. Each of thepivoted outer sections is guided by a pivoted slide bar, and the twopivoted slide bars can be adjusted by a positioning device to the sameangle in opposite directions.

If both adjustable slide bars are swung from their null or neutralpositions, one of the outer conveyer suction grippers executes anadditional oscillating motion in the transport direction, and the other,outer conveyer suction gripper executesan oscillatory movement of thesame magnitude but in the opposite direction. The transported sheetthereby rotates about the vertical axis of the middle-suction gripper,which is designed as a drop or gravity gripper. Practically no lateralor longitudinal displacement of the transported sheet occurs.

In further advantageous embodiment of the present invention drive holdermeans are pivoted at the free end of an oscillating crank of aneccentric drive, such drive holder means extending in the direction ofthe sheet transport and being guided along a straight line path by theslide bar. The carrier bar of the conveyer suction gripper is arrangedat the free end of the drive holder means. This device permits thereliable processing of the largest sheet sizes as the distance of theconveyer suction grippers from the rear sheet edge is substantiallygreater than that which can be chosen with conventional suction heads.

In a preferred embodiment of the invention the slide bars are providedin the form of U-shaped guide rails which extend in the direction of thesheet transport and which have an arc-like curvature. The arc-likecurva-.

ture compensates for the influence which the crank oscillation mightotherwise have on the vertical movement and guidance of the conveyersuction grippers, which tends to be accentuated or amplified because offor the invention are set forth in the appended claims.

Although the invention is illustrated and described in relationship tospecific embodiments, it is nevertheless not intended to be limited tothe details shown, since various modifications and structural changesmay be made therein without departing from the spirit of the inventionand within the scope and rang of equivalents of the claims.

The construction and method of operation-of the invention, however,together with additional objects and advantages thereof will be bestunderstood from the following description of specific embodiments whenread inconnection with the accompanying drawings, in which:

FIG. 1 is a partial elevational view of a suction head disposed above astack of sheets which are to be fed by the suction head.

FIG. 2 is a partial plan view of the suction head shown in FIG. 1.

FIG. 3 is a plan view, partially in section, showing the variousoperating. elements of the suction head according to one embodiment ofthe invention.

FIG. 4 is an elevation view of the various operating elements shown inFIG. 3.

Referring to the drawings, there is shown a suction head 2 arrangedabove a stack of sheets 1 of a printing machine (not shown). The suctionhead 2 is disposed centrally, considered in a lateral direction, and inthe region of the rear edge of the stack of sheets 1. The height of thestack of sheets 1 can be adjusted by various means (not shown) forexample by pneumatically or electrically operated devices. The suctionhead 2 always feeds the top sheet of the stack of sheets 1 to furthertransport means which consists of a tape roller 8 and timing rolls 9.The aforementioned feeding is effected with the cooperation of a sensingfoot 3, separator suction grippers 4 and conveyer suction grippers5,6,7.

The conveyer suction grippers 5 to 7 are attached to a carrier bar 10which is divided into three sections,

namely, a central rigid part 11 and the two outer carrier tubes 12 and13 which are rotatably mounted on the outer longitudinal ends of thecentral rigid part 11.

The conveyer suction gripper 6 is designed as a drop or gravity gripperand is mounted on the central bar section 11. The suction gripper 6situated exactly along the center line of the suction head 2 as shown inFIG. 2. The conveyer suction gripper 5 is attached to the carrier tube13, and the conveyer suction gripper 7 to the carrier tube 12. Bothconveyer suction grippers 5 and -7 are also designed as dropor gravitygrippers. The central bar section 11 is operatively connected by meansof two brackets 14 and 15 to a shaft 16 which is mounted in sleeve,bearings 18 and which are pivoted at the free end of a conventionaloscillating crank 17 of an eccentric drive (not shown). A support arm 19is fixed to the bracket 15 at about halfway along the length of bracket15. The support arm 19 projects vertically and rotatably carries aroller 20 which travels in a guide rail 21. The guide rail .21 issecured to a housing 22 of the suction head 2. As can be seen in FIG. 4,the guide rail 21 is curved in arc fashion in such a manner tocompensate the swinging motion of the conveyer suction gripper 6 whichwould otherwise be caused by the oscilatory motion of the crank 17.

A guide lever 23 is secured to the carrier tube 12 and the free end ofthe guide lever carriers a guide roller 24 which travels in a U-shapedguide rail 25. The guide rail 25 is pivoted at its rear end about afixed horizontal axis 30, the angular position of the guide rail 25relative to the horizontal can be changed by a setting device 26.

'of the suction head housing 22 and is pivoted at 52, 53

respectively to the two guide rails 25 and 29. The arrangement is suchthat any pivotal movement of the U- shaped guide rail 25 about axis 31is transmitted to the other U-shaped guide rail 29. For example, whenthe U-shaped guide rail 25 swings upwardly, the opposite U-shaped guiderail 29 swings downward by the same angle. The setting device 26 isprovided with a hand wheel 33 above the suction head housing 22 and isoperable to pivot the guide rail 25 upwardly or downwardly about fixedpivot axis 30.

The two.U-shaped.guide rails 25 and 29 are also curved in the form ofanarc like the guide rail 21 in such a manner that the conveyer suctiongrippers 7 and 5 secured to the outer carrier tubes 12 and 13 aremaintained in a vertical disposition during the oscillating movement ofthe crank 17.

The separator suction gripper 4 and the conveyer suction grippers 5 to 7are operatively connected to and in communication with a rotary valve 34mounted on the suction head 2 by means of hose lines 35. Two other hoses36 connect the rotary valve 34 with a blower or other pressure or vacuumgenerator. A further hose 50 leads from the rotary valve 34 to a blowerrod 38 at which loosening blowers 39 as well as a stripper brush 40 aremounted. Another hose 37 leads to the sensing foot 3.

The operation of the apparatus hereinabove described is as follows. If asheet transported by the conveyer suction grippers 5 to 7 isfed askew tothe transport means 8, 9 for example, because the pile is not cut squareor the surface of the pile is different or out of alignment as indicatedby the sheet 41 in FIG. 2 for example, the guide rail 25 is pivotedabout the horizontal axis 30 by means-ofthe hand wheel 33 via thesetting device '26. When this occurs the opposite guide rail 29 ispivoted by the same angle in the opposite direction as previouslyexplained. The adjustment takes place to such an extent that the twoouter conveyer suction grippers 5 and '7 execute during the transport ofthe sheet, on the basis of the adjustment of their guide rails 25 and29, oscillating movements in opposite directions of such magnitude thatthe tilt of the sheet is cancelled by rotation of suction grippers 5 and7 each the same amount about the-middle conveyer suction gripper 6. As aresult the sheet 41 is passed on to the roller 8 and the timing rolls 9in proper alignment. The aforementioned oscilating movement of the outerconveyer suction grippers 5 and 7 about the suction gripper 6 startswhen the conveyer suction grippers 5 and 7 are in their rear positionindicated at 42 in FIG. 2 and has its maximum extent in the frontposition of the conveyer suction grippers as indicated at 43 in FIG. 2.Accordingly the suction cups of the conveyer suction gripper 5 and 7always occupy the same position in their rear position 42 as is the caseof the suction cup of the not-rotatable central conveyer suction gripper6. It will be seen that the aforementioned oscillating movement isachieved because the guide rails 25 and 29 are pivotally moved aboutaxis 30 in opposite pivotal directions. Due to the fact that the twoouter conveyer suction grippers 5 and 7 execute opposite oscillatingmotions, the oscillation movement of each conveyer suction gripper 5 or7 needs to be only half as large as if the oscillating motion wascarried out with only one conveyer suction gripper as in known devices.Because all the conveyer suction grippers are designed as-gravitysuction grippers, the suction cup of the central conveyer suctiongripper 6 can rotate about its vertical axis, so that the sheet to bealigned can be swung around such vertical axis without the formation ofcreases. The use of three conveyer suction grippers has anotheradvantage in that the support air discharging from the sensing foot 3can lift the front edge of the sheet 41 reliably onto the belt roller 8.

The invention is not limited to the illustrated embodiment. For example,the invention may be modified in such a manner to provide a leverlinkage instead of the guide arms 23 and 27, such that the conveyersuction grippers 5 and 7 can be advanced still further in the directiontoward the belt roller 8 and timing rolls 9.

I claim:

1. Sheet feeding apparatus for printing presses and the like in whichsheets are lifted from a stack and transported towards a sheet feeddevice, comprising carrier means, operable means for moving said carriermeans between apick-up position and a feed position, said carrier meanscomprising a carrier bar having a central section and two outer sectionsrotatably mounted on either side of said central section, two outersuction grippers, one carried on each of said outer sections, firstslide bar means carried by each of said outer sections, and positionalmeans comprising a rocker arm operable to adjust each of said slide barmeans to the same angular extent but in opposite directions so that saidslide bar'means cause rotation of the outer sections through equal butoppositely directed angles relative to the central section duringforward movement of the carrier bar, and adjustment means for saidrocker arm, said outer suction grippers being operable thereby to aligna sheet as the latter is transported from said stack towards said sheetfeed device.

2. Sheetfeeding apparatus according to claim 1 a central suction grippercarried on said central section of said carrier bar, said centralsuction gripper and said outer suction grippers being generally alignedalong a straight line extending perpendicular to said path of movementof said carrier means when the latter is in said pick-up position, saidpositional means being operable to vary the path of said slide bar meansso that said outer suction grippers and said central suction gripper arealigned along a straight line which extends at an acute angle relativeto said path of movement of said carrier means when the latter is insaid feed position.

3. Sheet feeding apparatus according to claim 2 wherein said meansoperable to vary the paths of said slide bar means comprise a pivotaldrive member pivotal back and forth about a pivot axis to impart a backand forth oscillating motion to said first slide bar means, said carriermeans comprising second slide bar means maintaining said central suctiongripper in a vertical plane disposition during said oscillating motionof said first slide bar means.

4. Sheet feeding apparatus according to claim 3 wherein said drivemember is a crank, having a free end oscillating along an arcuate path,drive holder means pivotally mounted on said free end of said crank andextending in the direction of sheet feed, second slide bar meansoperatively associated with said drive holder means to providerectiliniearly movement of the free ends of said drive holder means,said carrier bar being disposed at said free end of said drive holdermeans whereby said carrier bar is subjected to a rectiliniear movement.

5. Sheet feeding apparatus according to claim 4 wherein said secondslide bar means comprises U- shaped guide rails extending generally inthe direction of sheet feed in an arcuate configuration.

6. Sheet feeding apparatus according to claim 5 wherein rollers aremounted on said drive holder means, said rollers being movably carriedin said U- shaped guide rails, 7. Sheet feeding apparatus according toclaim 1 wherein said first mentioned slide bar means comprises U-shapedguide rails extending generally'in the direction of sheet feed in anarcuate configuration. I

8. Sheet feeding apparatus according to claim 7 wherein said firstmentioned slide bar means comprises levers attached to said outersections of said carrier bar, said levers having mounted thereon rollerswhich are movably carried in said U-shaped guide rails.

1. Sheet feeding apparatus for printing presses and the like in whichsheets are lifted from a stack and transported towards a sheet feeddevice, comprising carrier means, operable means for moving said carriermeans between a pick-up position and a feed position, said carrier meanscomprising a carrier bar having a central section and two outer sectionsrotatably mounted on either side of said central section, two outersuction grippers, one carried on each of said outer sections, firstslide bar means carried by each of said outer sections, and positionalmeans comprising a rocker arm operable to adjust each of said slide barmeans to the same angular extent but in opposite directions so that saidslide bar means cause rotation of the outer sections through equal butoppositely directed angles relative to the central section duringforward movement of the carrier bar, and adjustment means for saidrocker arm, said outer suction grippers being operable thereby to aligna sheet as the latter is transported from said stack towards said sheetfeed device.
 2. Sheet feeding apparatus according to claim 1 a centralsuction gripper carried on said central section of said carrier bar,said central suction gripper and said outer suction grippers beinggenerally aligned along a straight line extending perpendicular to saidpath of movement of said carrier means when the latter is in saidpick-up position, said positional means being operable to vary the pathof said slide bar means so that said outer suction grippers and saidcentral suction gripper are aligned along a straight line which extendsat an acute angle relative to said path of movement of said carriermeans when the latter is in said feed position.
 3. Sheet feedingapparatus according to claim 2 wherein said means operable to vary thepaths of said slide bar means comprise a pivotal drive member pivotalback and forth about a pivot axis to impart a back and forth oscillatingmotion to said first slide bar means, said carrier means comprisingsecond slide bar means maintaining said central suction gripper in avertical plane disposition during said oscillating motion of said firstslide bar means.
 4. Sheet feeding apparatus according to claim 3 whereinsaid drive member is a crank, having a free end oscillating along anarcuate path, drive holder means pivotally mounted on said free end ofsaid crank and extending in the direction of sheet feed, second slidebar means operatively associated with said drive holder means to providerectiliniearly movement of the free ends of said drive holder means,said carrier bar being disposed at said free end of said drive holdermeans whereby said carrier bar is subjected to a rectiliniear movement.5. Sheet feeding apparatus according to claim 4 wherein said secondslide bar means comprises U-shaped guide rails extending generally inthe direction of sheet feed in an arcuate configuration.
 6. Sheetfeeding apparatus according to claim 5 wherein rollers are mounted onsaid drive holder means, said rollers being movably carried in saidU-shaped guide rails.
 7. Sheet feeding apparatus according to claim 1wherein said first mentioned slide bar means comprises U-shaped guiderails extending generally in the direction of sheet feed in an arcuateconfiguration.
 8. Sheet feeding apparatus according to claim 7 whereinsaid first mentioned slide bar means comprises levers attached to saidouteR sections of said carrier bar, said levers having mounted thereonrollers which are movably carried in said U-shaped guide rails.